Shrouded Attrition Nozzle and Method of Use Thereof

Abstract

A shrouded attrition nozzle for use in fluidized bed jet attrition. The nozzle comprises a shroud surrounding the nozzle and extending upwardly from the nozzle tip. The shroud is sized so as not to interfere with the periphery of the jet emitted from the nozzle and may be cylindrical or inverted frustoconical in shape. When a desired spacing is achieved between the periphery of the jet and the shroud, fluidizable material enters the interior of the shroud from the open end, moving countercurrently towards the nozzle tip. A disengagement of fluidization gas from fluidizable material occurs and an increased entrainment of solids in the jet leads to improvements in grinding efficiency. The result is a reduction in jet flowrate and fluidization gas wastage, which reduces overall energy requirements for attrition. A method of causing attrition of a fluidizable material using the shrouded nozzle is also disclosed.

1 . A shrouded attrition nozzle for use in a vessel containing a fluidized bed of a fluidizable media, the nozzle comprising:
 (a) a nozzle body having a nozzle height and an orifice at one end with an inner diameter for emitting a high velocity gas jet into the fluidized bed, the gas jet having a jet angle between a periphery of the jet and a normal to the orifice;   (b) a shroud having a shroud height, an interior within which the nozzle body is centrally located, an interior diameter, a first end that is open and a second end that prevents passage of the media into the interior;   (c) the relationship between the nozzle height (h), the orifice inner diameter (d), the jet angle (θ), the shroud height (H) and the shroud interior diameter (D) defined by,   
       
         
           
             
               C 
               = 
               
                 
                   
                     D 
                     - 
                     d 
                   
                   2 
                 
                 - 
                 
                   
                     ( 
                     
                       H 
                       - 
                       h 
                     
                     ) 
                   
                    
                   
                     tan 
                      
                     
                       ( 
                       θ 
                       ) 
                     
                   
                 
               
             
           
         
         
           wherein C represents the distance between the periphery of the jet and the shroud across the first end and is from 1 to 100 mm. 
         
       
     
     
         2 . The shrouded attrition nozzle of  claim 1 , wherein the second end is closed and wherein the shroud is attached to the nozzle body. 
     
     
         3 . The shrouded attrition nozzle of  claim 1 , wherein the second end abuts an interior surface of the vessel when the nozzle is in use, thereby preventing passage of the fluidizable media between the surface and the second end. 
     
     
         4 . The shrouded attrition nozzle of  claim 1 , wherein the fluidizable media is able to enter the interior of the shroud only through the first end. 
     
     
         5 . The shrouded attrition nozzle of  claim 1 , wherein the shroud is cylindrical or inverted frustoconical in shape. 
     
     
         6 . The shrouded attrition nozzle of  claim 1 , wherein the jet is inverted conical, inverted frustoconical or fan shaped. 
     
     
         7 . The shrouded attrition nozzle of  claim 1 , wherein the jet angle (θ) is from 10 to 20 degrees. 
     
     
         8 . The shrouded attrition nozzle of  claim 1 , wherein C is from 5 to 50 mm. 
     
     
         9 . The shrouded attrition nozzle of  claim 1 , wherein the jet angle (θ) is from 12 to 18 degrees and wherein C is from 5 to 20 mm. 
     
     
         10 . The shrouded attrition nozzle of  claim 1 , wherein the shroud interior diameter (D) is from 30 to 90 mm. 
     
     
         11 . The shrouded attrition nozzle of  claim 1 , wherein the shroud height (H) is from 10 to 80 mm. 
     
     
         12 . A method of causing attrition of a fluidizable media comprising:
 (a) providing a vessel containing a fluidizable media and a shrouded attrition nozzle comprising a nozzle body having an orifice at one end and a shroud having an interior within which the nozzle body is centrally located, a first end that is open and a second end that prevents passage of the media into the interior;   (b) creating a fluidized bed by flowing a fluidizing gas through the fluidizable media within the vessel;   (c) directing a flow of gas through the nozzle body;   (d) emitting a high velocity gas jet from the orifice into the fluidized bed;   (e) admitting the fluidizable media into the interior of the shroud through the first end; and,   (f) entraining the admitted media with the jet at high velocity into the fluidized bed, thereby causing attrition of the media.   
     
     
         13 . The method of  claim 12 , wherein the fluidizable media is admitted into the interior of the shroud only through the first end. 
     
     
         14 . The shrouded attrition nozzle of  claim 12 , wherein the nozzle is mounted horizontally 
     
     
         15 . The shrouded attrition nozzle of  claim 12 , wherein the nozzle is mounted vertically 
     
     
         16 . The method of  claim 12 , wherein the vessel further comprises a target spaced apart from the first end of the shroud and transverse to the jet. 
     
     
         17 . The method of  claim 12 , wherein the vessel further comprises a draft tube spaced apart from the first end of the shroud and aligned with the jet and wherein the admitted media is entrained with the jet into the draft tube. 
     
     
         18 . The method of  claim 17 , wherein the draft tube is located from 10 to 150 mm from the orifice. 
     
     
         19 . The method of  claim 12 , wherein the fluidizing gas disengages from the fluidizable material within the interior of the shroud. 
     
     
         20 . The method of  claim 12 , wherein the fluidizable material moves countercurrent to the jet within the shroud toward the orifice.